Osteopontin is expressed in human aortic valvular lesions

Osteopontin stabilization and collagen containment slows amorphous calcium phosphate transformation during human aortic valve leaflet calcification

Calcification of aortic valve leaflets is a growing mortality threat for the 18 million human lives claimed globally each year by heart disease. Extensive research has focused on the cellular and molecular pathophysiology associated with calcification, yet the detailed composition, structure, distribution and etiological history of mineral deposition remains unknown. Here transdisciplinary geology, biology and medicine (GeoBioMed) approaches prove that leaflet calcification is driven by amorphous calcium phosphate (ACP), ACP at the threshold of transformation toward hydroxyapatite (HAP) and cholesterol biomineralization. A paragenetic sequence of events is observed that includes: (1) original formation of unaltered leaflet tissues: (2) individual and coalescing 100's nm- to 1 μm-scale ACP spherules and cholesterol crystals biomineralizing collagen fibers and smooth muscle cell myofilaments; (3) osteopontin coatings that stabilize ACP and collagen containment of nodules preventing exposure to the solution chemistry and water content of pumping blood, which combine to slow transformation to HAP; (4) mm-scale nodule growth via ACP spherule coalescence, diagenetic incorporation of altered collagen and aggregation with other ACP nodules; and (5) leaflet diastole and systole flexure causing nodules to twist, fold their encasing collagen fibers and increase stiffness. These in vivo mechanisms combine to slow leaflet calcification and establish previously unexplored hypotheses for testing novel drug therapies and clinical interventions as viable alternatives to current reliance on surgical/percutaneous valve implants.

Exploring molecular profiles of calcification in aortic vascular smooth muscle cells and aortic valvular interstitial cells

Cardiovascular calcification can occur in vascular and valvular structures and is commonly associated with calcium deposition and tissue mineralization leading to stiffness and dysfunction. Patients with chronic kidney disease and associated hyperphosphatemia have an elevated risk for coronary artery calcification (CAC) and calcific aortic valve disease (CAVD). However, there is mounting evidence to suggest that the susceptibility and pathobiology of calcification in these two cardiovascular structures may be different, yet clinically they are similarly treated. To better understand diversity in molecular and cellular processes that underlie hyperphosphatemia-induced calcification in vascular and valvular structures, we exposed aortic vascular smooth muscle cells (AVSMCs) and aortic valve interstitial cells (AVICs) to high (2.5 mM) phosphate (Ph) conditions in vitro, and examined cell-specific responses. To further identify hyperphosphatemic-specific responses, parallel studies were performed using osteogenic media (OM) as an alternative calcific stimulus. Consistent with clinical observations made by others, we show that AVSMCs are more susceptible to calcification than AVICs. In addition, bulk RNA-sequencing reveals that AVSMCs and AVICs activate robust ossification-programs in response to high phosphate or OM treatments, however, the signaling pathways, cellular processes and osteogenic-associated markers involved are cell- and treatment-specific. For example, compared to VSMCs, VIC-mediated calcification involves biological processes related to osteo-chondro differentiation and down regulation of 'actin cytoskeleton'-related genes, that are not observed in VSMCs. Furthermore, hyperphosphatemic-induced calcification in AVICs and AVSMCs is independent of P13K signaling, which plays a role in OM-treated cells. Together, this study provides a wealth of information suggesting that the pathogenesis of cardiovascular calcifications is significantly more diverse than previously appreciated.

Sam68 promotes osteogenic differentiation of aortic valvular interstitial cells by TNF-α/STAT3/autophagy axis

Calcified aortic valve disease (CAVD) is a major non-rheumatic heart valve disease in the world, with a high mortality rate and without suitable pharmaceutical therapy due to its complex mechanisms. Src-associated in mitosis 68-KD (Sam68), an RNA binding protein, has been reported as a signaling adaptor in numerous signaling pathways (Huot in Mol Cell Biol, 29(7), 1933-1943, 2009), particularly in inflammatory signaling pathways. The effects of Sam68 on the osteogenic differentiation process of hVICs and its regulation on signal transducer and activator of transcription 3 (STAT3) signaling pathway have been investigated in this study. Human aortic valve samples detection found that Sam68 expression was up-regulated in human calcific aortic valves. We used tumor necrosis factor α (TNF-α) as an activator for osteogenic differentiation in vitro and the result indicated that Sam68 was highly expressed after TNF-α stimulation. Overexpression of Sam68 promoted osteogenic differentiation of hVICs while Sam68 knockdown reversed this effect. Sam68 interaction with STAT3 was predicted by using String database and was verified in this study. Sam68 knockdown reduced phosphorylation of STAT3 activated by TNF-α and the downstream gene expression, which further influenced autophagy flux in hVICs. STAT3 knockdown alleviated the osteogenic differentiation and calcium deposition promoted by Sam68 overexpression. In conclusion, Sam68 interacts with STAT3 and participates in its phosphorylation to promote osteogenic differentiation of hVICs to induce valve calcification. Thus, Sam68 may be a new therapeutic target for CAVD. Regulatory of Sam68 in TNF-α/STAT3/Autophagy Axis in promoting osteogenesis of hVICs.

Diabetes mellitus and aortic stenosis head to head: toward personalized medicine in patients with both pathologies

Diabetes mellitus (DM) and calcific aortic stenosis (CAS) are common morbidities in the elderly, which are both chronic, progressive and often concomitant diseases. Several studies revealed that DM increases the risk of developing severe CAS, yet clear information about the relationship between both these diseases and the influence of DM on the progression of CAS is currently lacking. To evaluate the effect of DM on aortic valves and on the process of calcification, and to achieve better patient management in daily clinical practice, we analysed calcified and noncalcified valve tissue from patients with severe CAS, with or without DM. A proteomic strategy using isobaric tags was adopted and the plasma concentrations of nine proteins were studied using 3 orthogonal methods and in a separate cell model. The differentially expressed proteins identified are implicated in biological processes like endopeptidase activity, lipid metabolism, coagulation, and fibrinolysis. The results obtained provide evidence that DM provokes changes in the proteome of aortic valves, affecting valve calcification. This finding may help enhance our understanding of the pathogenesis of CAS and how DM affects the evolution of this condition, an important step in identifying targets to personalize the treatment of these patients.

Hydrogen sulfide as an anti-calcification stratagem in human aortic valve: Altered biogenesis and mitochondrial metabolism of H2S lead to H2S deficiency in calcific aortic valve disease

Hydrogen sulfide (H₂S) was previously revealed to inhibit osteoblastic differentiation of valvular interstitial cells (VICs), a pathological feature in calcific aortic valve disease (CAVD). This study aimed to explore the metabolic control of H₂S levels in human aortic valves. Lower levels of bioavailable H₂S and higher levels of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) were detected in aortic valves of CAVD patients compared to healthy individuals, accompanied by higher expression of cystathionine γ-lyase (CSE) and same expression of cystathionine β-synthase (CBS). Increased biogenesis of H₂S by CSE was found in the aortic valves of CAVD patients which is supported by increased production of lanthionine. In accordance, healthy human aortic VICs mimic human pathology under calcifying conditions, as elevated CSE expression is associated with low levels of H₂S. The expression of mitochondrial enzymes involved in H₂S catabolism including sulfide quinone oxidoreductase (SQR), the key enzyme in mitochondrial H₂S oxidation, persulfide dioxygenase (ETHE1), sulfite oxidase (SO) and thiosulfate sulfurtransferase (TST) were up-regulated in calcific aortic valve tissues, and a similar expression pattern was observed in response to high phosphate levels in VICs. AP39, a mitochondria-targeting H₂S donor, rescued VICs from an osteoblastic phenotype switch and reduced the expression of IL-1β and TNF-α in VICs. Both pro-inflammatory cytokines aggravated calcification and osteoblastic differentiation of VICs derived from the calcific aortic valves. In contrast, IL-1β and TNF-α provided an early and transient inhibition of VICs calcification and osteoblastic differentiation in healthy cells and that effect was lost as H₂S levels decreased. The benefit was mediated via CSE induction and H₂S generation. We conclude that decreased levels of bioavailable H₂S in human calcific aortic valves result from an increased H₂S metabolism that facilitates the development of CAVD. CSE/H₂S represent a pathway that reverses the action of calcifying stimuli.

Crosstalk between myofibroblasts and macrophages: A regulative factor of valvular fibrosis in calcific aortic valve disease

Inflammation and fibrosis are highly correlated with the progression of calcific aortic valve disease (CAVD). As one of the differentiated forms of valvular interstitial cells, myofibroblasts play a critical role in CAVD's development as do macrophages. Although numerous studies have been conducted on them separately, their communication and interaction remain unclear. We used porcine aortic valves to isolate valve interstitial cells (VICs). VICs were induced to differentiate into myofibroblasts by transforming growth factor-β1 (TGF-β1). After successful activation was determined, the myofibroblast-conditioned medium (CM) was collected and used to act on RAW264.7, a macrophage cell line. A migration and adhesion assay estimated the recruitment capability of myofibroblasts on macrophages. We used flow cytometry, quantitative polymerase chain reaction (qPCR), and Western blot analysis to investigate myofibroblasts' polarity promotion function in macrophages. Finally, we used macrophage-CM on VICs to explore the differentiation induction function of polarized macrophages. Myofibroblast marker alpha-smooth muscle actin and M2 macrophage marker CD163 were detected as upregulated in CAVD patients, and their expression has a certain correlation. The Smad3/HA/CD44 axis activated the differentiation of myofibroblasts by Western blot. The myofibroblast-CM can promote chemotaxis and adhesion of macrophages through protein kinase B/chemokine (C-C motif) ligand5 and Smad3/HA/CD44, respectively. Hyaluronic acid (HA) inside the myofibroblast-CM stimulates macrophages to polarize into M2 macrophages. In turn, M2 macrophage-CM has the promotive ability to activate myofibroblasts but fails to induce the osteoblast differentiation of VICs directly. The crosstalk between myofibroblasts and macrophages causes the excessive activation of myofibroblasts. This positive feedback loop may play a vital role in CAVD progression.

Myringosclerosis as a predictor of the requirement for a permanent pacemaker in patients with drug-related atrioventricular block

AIMS

Drug-related atrioventricular block (DR-AVB) may develop in patients with underlying latent degenerative conduction disorders, especially with antiarrhythmics and antihypertensives. Although, according to the current guidelines, reversal is achieved with cessation of the inducing agent, this is not the case for nearly half of the patients. The pathophysiological processes of DR-AVB and myringosclerosis include systemic inflammation and degeneration. This study investigated the role of myringosclerosis in predicting irreversible high-grade DR-AVB despite drug cessation.

METHODS

This observational, non-randomized, prospective study involved 152 patients with high-grade DR-AVB, 72 of whom had reversible DR-AVB and 80 had irreversible DR-AVB and required permanent pacemakers. The patients' demographic, clinical, echocardiographic, and laboratory characteristics were recorded. Otoscopic tympanic membrane examinations for myringosclerosis were performed.

RESULTS

There were no major differences in demographic, echocardiographic or laboratory characteristics between the two groups or previous medications. The median monitoring time with a temporary pacemaker was significantly longer in the irreversible than in the reversible group (5 [4-7] days vs. 2 [1-5] days; P<0.001). The incidence of myringosclerosis was significantly higher in the irreversible than in the reversible group (61.3% vs. 22.2%; P=0.001). Multivariate logistic regression analysis showed that myringosclerosis was an independent predictor of irreversible DR-AVB (odds ratio: 1.703, 95% confidence interval: 1.194-3.058; P=0.01).

CONCLUSION

Myringosclerosis is a readily available, inexpensive, and non-invasive assessment and is a marker of inflammation and degeneration that can predict irreversible DR-AVB.

Sex-Differences in Aortic Stenosis: Mechanistic Insights and Clinical Implications

Objective

We aim to analyse sex-specific differences in aortic valves (AVs) and valve interstitial cells (VICs) from aortic stenosis (AS) patients.

Approach and Results

238 patients with severe AS undergoing surgical valve replacement were recruited. Two hundred and two AVs (39.1% women) were used for ex vivo analyses and 36 AVs (33.3% women) for in vitro experiments. AVs from men presented increased levels of the inflammatory molecules interleukin (IL)-1β, IL-6, Rantes, and CD45. Oxidative stress (eNOS, myeloperoxidase, malondialdehyde and nitrotyrosine) was upregulated in male AVs. Concerning fibrosis, similar levels of collagen type I, decreased levels of collagen type III and enhanced fibronectin, active Lox-1 and syndecan-1 expressions were found in AVs from men compared with women. Extracellular matrix (ECM) remodeling was characterized by reduced metalloproteinase-1 and 9 expression and increased tissue inhibitor of metalloproteinase-2 expression in male AVs. Importantly, osteogenic markers (bone morphogenetic protein-9, Rank-L, osteopontin, periostin, osteocalcin and Sox-9) and apoptosis (Bax, Caspase 3, p53, and PARP1) were enhanced in AVs from men as compared to women. Isolated male VICs presented higher myofibroblast-like phenotype than female VICs. Male VICs exhibited increased inflammatory, oxidative stress, fibrotic, apoptosis and osteogenic differentiation markers.

Conclusions

Our results suggest that the mechanisms driving the pathogenesis of AS could be different in men and women. Male AVs and isolated VICs presented more inflammation, oxidative stress, ECM remodeling and calcification as compared to those from women. A better knowledge of the pathophysiological pathways in AVs and VICs will allow the development of sex-specific options for the treatment of AS.

Calcium-Dependent Cytosolic Phospholipase A2α as Key Factor in Calcification of Subdermally Implanted Aortic Valve Leaflets

Calcium-dependent cytosolic phospholipase A2α (cPLA2α) had been previously found to be overexpressed by aortic valve interstitial cells (AVICs) subjected to in vitro calcific induction. Here, cPLA2α expression was immunohistochemically assayed in porcine aortic valve leaflets (iAVLs) that had undergone accelerated calcification subsequent to 2- to 28-day-long implantation in rat subcutis. A time-dependent increase in cPLA2α-positive AVICs paralleled mineralization progression depending on dramatic cell membrane degeneration with the release of hydroxyapatite-nucleating acidic lipid material, as revealed by immunogold particles decorating organelle membranes in 2d-iAVLs, as well as membrane-derived lipid byproducts in 7d- to 28d-iAVLs. Additional positivity was detected for (i) pro-inflammatory IL-6, mostly exhibited by rat peri-implant cells surrounding 14d- and 28d-iAVLs; (ii) calcium-binding osteopontin, with time-dependent increase and no ossification occurrence; (iii) anti-calcific fetuin-A, mostly restricted to blood plasma within vessels irrorating the connective envelopes of 28d-iAVLs; (iv) early apoptosis marker annexin-V, limited to sporadic AVICs in all iAVLs. No positivity was found for either apoptosis executioner cleaved caspase-3 or autophagy marker MAP1. In conclusion, cPLA2α appears to be a factor characterizing AVL calcification concurrently with a distinct still uncoded cell death form also in an animal model, as well as a putative target for the prevention and treatment of calcific valve diseases.

Role of Extracellular Vesicles as Potential Diagnostic and/or Therapeutic Biomarkers in Chronic Cardiovascular Diseases

Cardiovascular diseases (CVDs) are the first cause of death worldwide. In recent years, there has been great interest in the analysis of extracellular vesicles (EVs), including exosomes and microparticles, as potential mediators of biological communication between circulating cells/plasma and cells of the vasculature. Besides their activity as biological effectors, EVs have been also investigated as circulating/systemic biomarkers in different acute and chronic CVDs. In this review, the role of EVs as potential diagnostic and prognostic biomarkers in chronic cardiovascular diseases, including atherosclerosis (mainly, peripheral arterial disease, PAD), aortic stenosis (AS) and aortic aneurysms (AAs), will be described. Mechanistically, we will analyze the implication of EVs in pathological processes associated to cardiovascular remodeling, with special emphasis in their role in vascular and valvular calcification. Specifically, we will focus on the participation of EVs in calcium accumulation in the pathological vascular wall and aortic valves, involving the phenotypic change of vascular smooth muscle cells (SMCs) or valvular interstitial cells (IC) to osteoblast-like cells. The knowledge of the implication of EVs in the pathogenic mechanisms of cardiovascular remodeling is still to be completely deciphered but there are promising results supporting their potential translational application to the diagnosis and therapy of different CVDs.

Metformin alleviates the calcification of aortic valve interstitial cells through activating the PI3K/AKT pathway in an AMPK dependent way

BACKGROUND

Calcific aortic valve disease (CAVD) is the most prevalent valvular disease worldwide. However, no effective treatment could delay or prevent the progression of the disease due to the poor understanding of its pathological mechanism. Many studies showed that metformin exerted beneficial effects on multiple cardiovascular diseases by mediating multiple proteins such as AMPK, NF-κB, and AKT. This study aims to verify whether metformin can inhibit aortic calcification through the PI3K/AKT signaling pathway.

METHODS

We first analyzed four microarray datasets to screen differentially expressed genes (DEGs) and signaling pathways related to CAVD. Then aortic valve samples were used to verify selected genes and pathways through immunohistochemistry (IHC) and western blot (WB) assays. Aortic valve interstitial cells (AVICs) were isolated from non-calcific aortic valves and then cultured with phosphate medium (PM) with or without metformin to verify whether metformin can inhibit the osteogenic differentiation and calcification of AVICs. Finally, we used inhibitors and siRNA targeting AMPK, NF-κB, and AKT to study the mechanism of metformin.

RESULTS

We screened 227 DEGs; NF-κB and PI3K/AKT signaling pathways were implicated in the pathological mechanism of CAVD. IHC and WB experiments showed decreased AMPK and AKT and increased Bax in calcific aortic valves. PM treatment significantly reduced AMPK and PI3K/AKT signaling pathways, promoted Bax/Bcl2 ratio, and induced AVICs calcification. Metformin treatment ameliorated AVICs calcification and apoptosis by activating the PI3K/AKT signaling pathway. AMPK activation and NF-κB inhibition could inhibit AVICs calcification induced by PM treatment; however, AMPK and AKT inhibition reversed the protective effect of metformin.

CONCLUSIONS

This study, for the first time, demonstrates that metformin can inhibit AVICs in vitro calcification by activating the PI3K/AKT signaling pathway; this suggests that metformin may provide a potential target for the treatment of CAVD. And the PI3K/AKT signaling pathway emerges as an important regulatory axis in the pathological mechanism of CAVD.

Organ Culture Model of Aortic Valve Calcification

A significant amount of knowledge has been gained with the use of cell-based assays to elucidate the mechanisms that mediate heart valve calcification. However, cells used in these studies lack their association with the extra-cellular matrix or the influence of other cellular components of valve leaflets. We have developed a model of calcification using intact porcine valve leaflets, that relies upon a biological stimulus to drive the formation of calcified nodules within the valve leaflets. Alizarin Red positive regions were formed in response to lipopolysaccharide and inorganic phosphate, which could be quantified when viewed under polarized light. Point analysis and elemental mapping analysis of electron microscope images confirmed the presence of nodules containing calcium and phosphorus. Immunohistochemical staining showed that the development of these calcified regions corresponded with the expression of RUNX2, osteocalcin, NF-kB and the apoptosis marker caspase 3. The formation of calcified nodules and the expression of bone markers were both inhibited by adenosine in a concentration-dependent manner, illustrating that the model is amenable to pharmacological manipulation. This organ culture model offers an increased level of tissue complexity in which to study the mechanisms that are involved in heart valve calcification.

Valvular Endothelial Cell Response to the Mechanical Environment-A Review

Heart valve leaflets are complex structures containing valve endothelial cells, interstitial cells, and extracellular matrix. Heart valve endothelial cells sense mechanical stimuli, and communicate amongst themselves and the surrounding cells and extracellular matrix to maintain tissue homeostasis. In the presence of abnormal mechanical stimuli, endothelial cell communication is triggered in defense and such processes may eventually lead to cardiac disease progression. This review focuses on the role of mechanical stimuli on heart valve endothelial surfaces-from heart valve development and maintenance of tissue integrity to disease progression with related signal pathways involved in this process.

Role of oxidative stress in calcific aortic valve disease and its therapeutic implications

Calcific aortic valve disease (CAVD) is the end result of active cellular processes that lead to the progressive fibrosis and calcification of aortic valve leaflets. In western populations, CAVD is a significant cause of cardiovascular morbidity and mortality, and in the absence of effective drugs, it will likely represent an increasing disease burden as populations age. As there are currently no pharmacological therapies available for preventing, treating, or slowing the development of CAVD, understanding the mechanisms underlying the initiation and progression of the disease is important for identifying novel therapeutic targets. Recent evidence has emerged of an important causative role for reactive oxygen species (ROS)-mediated oxidative stress in the pathophysiology of CAVD, inducing the differentiation of valve interstitial cells into myofibroblasts and then osteoblasts. In this review, we focus on the roles and sources of ROS driving CAVD and consider their potential as novel therapeutic targets for this debilitating condition.

New calcification model for intact murine aortic valves

Calcific aortic valve disease (CAVD) is a common progressive disease of the aortic valves, for which no medical treatment exists and surgery represents currently the only therapeutic solution. The development of novel pharmacological treatments for CAVD has been hampered by the lack of suitable test-systems, which require the preservation of the complex valve structure in a mechanically and biochemical controllable system. Therefore, we aimed at establishing a model which allows the study of calcification in intact mouse aortic valves by using the Miniature Tissue Culture System (MTCS), an ex vivo flow model for whole mouse hearts. Aortic valves of wild-type mice were cultured in the MTCS and exposed to osteogenic medium (OSM, containing ascorbic acid, β-glycerophosphate and dexamethasone) or inorganic phosphates (PI). Osteogenic calcification occurred in the aortic valve leaflets that were cultured ex vivo in the presence of PI, but not of OSM. In vitro cultured mouse and human valvular interstitial cells calcified in both OSM and PI conditions, revealing in vitro-ex vivo differences. Furthermore, endochondral differentiation occurred in the aortic root of ex vivo cultured mouse hearts near the hinge of the aortic valve in both PI and OSM conditions. Dexamethasone was found to induce endochondral differentiation in the aortic root, but to inhibit calcification and the expression of osteogenic markers in the aortic leaflet, partly explaining the absence of calcification in the aortic valve cultured with OSM. The osteogenic calcifications in the aortic leaflet and the endochondral differentiation in the aortic root resemble calcifications found in human CAVD. In conclusion, we have established an ex vivo calcification model for intact wild-type murine aortic valves in which the initiation and progression of aortic valve calcification can be studied. The in vitro-ex vivo differences found in our studies underline the importance of ex vivo models to facilitate pre-clinical translational studies.

[Aortic stenosis-which diagnostic algorithms and which treatment?]

The progress in cardiology during the last 50 years can best be studied by looking at the diagnostics and treatment of patients with aortic valve stenosis. Previously, the clinical examination, electrocardiography (ECG) and chest X‑ray were used before heart catheterization, which included a transseptal puncture to complete the indications for surgery in young patients. Nowadays, echocardiography, often combined with a dobutamine stress test, is the primary diagnostic tool to which computed tomography for quantification of valve calcification and cardiac magnetic resonance imaging can be of additive value. The treatment of severe aortic valve stenosis is no longer only treated by aortic valve replacement but transluminal aortic valve implantation also represents a new therapeutic option. The change in the age groups of treated patients is also noteworthy. Surgery is recommended for patients under 75 years old but for older patients, especially those with a high risk, interventional catheter-assisted treatment is preferred.

Hydrogen sulfide inhibits aortic valve calcification in heart via regulating RUNX2 by NF-κB, a link between inflammation and mineralization

Introduction

Hydrogen sulfide (H₂S) was revealed to inhibit aortic valve calcification and inflammation was implicated in the pathogenesis of calcific aortic valve disease (CAVD).

Objectives

We investigate whether H₂S inhibits mineralization via abolishing inflammation.

Methods and results

Expression of pro-inflammatory cytokines, interleukin-1β (IL-1β) and tumor necrosis factor α (TNF-α) were increased in patients with CAVD and in calcified aortic valve of ApoE-/- mice. Administration of H_{2 2}S releasing donor (4-methoxyphenyl piperidinylphosphinodithioc acid (AP72)) exhibited inhibition on both calcification and inflammation in aortic valve of apolipoprotein E knockout mice (ApoE-/-) mice is reflected by lowering IL-1β and TNF-α levels. Accordingly, AP72 prevented the accumulation of extracellular calcium deposition and decreased nuclear translocation of nuclear factor-κB (NF-κB) in human valvular interstitial cells (VIC). This was also accompanied by reduced cytokine response. Double-silencing of endogenous H₂S producing enzymes, Cystathionine gamma-lyase (CSE) and Cystathionine beta-synthase (CBS) in VIC exerted enhanced mineralization and higher levels of IL-1β and TNF-α. Importantly, silencing NF-κB gene or its pharmacological inhibition prevented nuclear translocation of runt-related transcription factor 2 (Runx2) and subsequently the calcification of human VIC. Increased levels of NF-κB and Runx2 and their nuclear accumulation occurred in ApoE-/- mice with a high-fat diet. Administration of AP72 decreased the expression of NF-κB and prevented its nuclear translocation in VIC of ApoE-/- mice on a high-fat diet, and that was accompanied by a lowered pro-inflammatory cytokine level. Similarly, activation of Runx2 did not occur in VIC of ApoE-/- mice treated with H₂S donor. Employing Stimulated Emission Depletion (STED) nanoscopy, a strong colocalization of NF-κB and Runx2 was detected during the progression of valvular calcification.

Conclusions

Hydrogen sulfide inhibits inflammation and calcification of aortic valve. Our study suggests that the regulation of Runx2 by hydrogen sulfide (CSE/CBS) occurs via NF-κB establishing a link between inflammation and mineralization in vascular calcification.

Aortic Valve Stenosis and Mitochondrial Dysfunctions: Clinical and Molecular Perspectives

Calcific aortic stenosis is a disorder that impacts the physiology of heart valves. Fibrocalcific events progress in conjunction with thickening of the valve leaflets. Over the years, these events promote stenosis and obstruction of blood flow. Known and common risk factors are congenital defects, aging and metabolic syndromes linked to high plasma levels of lipoproteins. Inflammation and oxidative stress are the main molecular mediators of the evolution of aortic stenosis in patients and these mediators regulate both the degradation and remodeling processes. Mitochondrial dysfunction and dysregulation of autophagy also contribute to the disease. A better understanding of these cellular impairments might help to develop new ways to treat patients since, at the moment, there is no effective medical treatment to diminish neither the advancement of valve stenosis nor the left ventricular function impairments, and the current approaches are surgical treatment or transcatheter aortic valve replacement with prosthesis.

Frontiers in positron emission tomography imaging of the vulnerable atherosclerotic plaque

Rupture of vulnerable atherosclerotic plaques leading to an atherothrombotic event is the primary driver of myocardial infarction and stroke. The ability to detect non-invasively the presence and evolution of vulnerable plaques could have a huge impact on the future identification and management of atherosclerotic cardiovascular disease. Positron emission tomography (PET) imaging with an appropriate radiotracer has the potential to achieve this goal. This review will discuss the biological hallmarks of plaque vulnerability before going on to evaluate and to present PET imaging approaches which target these processes. The focus of this review will be on techniques beyond [18F]FDG imaging, some of which are clinically advanced, and others which are on the horizon. As inflammation is the primary driving force behind atherosclerotic plaque development, we will predominantly focus on approaches which either directly, or indirectly, target this process.

The biology of vascular calcification

Vascular calcification (VC), characterized by different mineral deposits (i.e., carbonate apatite, whitlockite and hydroxyapatite) accumulating in blood vessels and valves, represents a relevant pathological process for the aging population and a life-threatening complication in acquired and in genetic diseases. Similarly to bone remodeling, VC is an actively regulated process in which many cells and molecules play a pivotal role. This review aims at: (i) describing the role of resident and circulating cells, of the extracellular environment and of positive and negative factors in driving the mineralization process; (ii) detailing the types of VC (i.e., intimal, medial and cardiac valve calcification); (iii) analyzing rare genetic diseases underlining the importance of altered pyrophosphate-dependent regulatory mechanisms; (iv) providing therapeutic options and perspectives.

Hydrogen sulfide inhibits calcification of heart valves; implications for calcific aortic valve disease

BACKGROUND AND PURPOSE

Calcification of heart valves is a frequent pathological finding in chronic kidney disease and in elderly patients. Hydrogen sulfide (H2 S) may exert anti-calcific actions. Here we investigated H2 S as an inhibitor of valvular calcification and to identify its targets in the pathogenesis.

EXPERIMENTAL APPROACH

Effects of H2 S on osteoblastic transdifferentiation of valvular interstitial cells (VIC) isolated from samples of human aortic valves were studied using immunohistochemistry and western blots. We also assessed H2S on valvular calcification in apolipoprotein E-deficient (ApoE-/- ) mice.

KEY RESULTS

In human VIC, H2 S from donor compounds (NaSH, Na2 S, GYY4137, AP67, and AP72) inhibited mineralization/osteoblastic transdifferentiation, dose-dependently in response to phosphate. Accumulation of calcium in the extracellular matrix and expression of osteocalcin and alkaline phosphatase was also inhibited. RUNX2 was not translocated to the nucleus and phosphate uptake was decreased. Pyrophosphate generation was increased via up-regulating ENPP2 and ANK1. Lowering endogenous production of H2 S by concomitant silencing of cystathionine γ-lyase (CSE) and cystathionine β-synthase (CBS) favoured VIC calcification. analysis of human specimens revealed higher Expression of CSE in aorta stenosis valves with calcification (AS) was higher than in valves of aortic insufficiency (AI). In contrast, tissue H2 S generation was lower in AS valves compared to AI valves. Valvular calcification in ApoE-/- mice on a high-fat diet was inhibited by H2 S.

CONCLUSIONS AND IMPLICATIONS

The endogenous CSE-CBS/H2 S system exerts anti-calcification effects in heart valves providing a novel therapeutic approach to prevent hardening of valves.

LINKED ARTICLES

This article is part of a themed section on Hydrogen Sulfide in Biology & Medicine. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.4/issuetoc.

Osteopontin in Bone Metabolism and Bone Diseases

Osteopontin (OPN), a secreted phosphoprotein, is a member of the small integrin-binding ligand N-linked glycoprotein (SIBLING) family of cell matrix proteins and participates in many biological activities. Studies have shown that OPN plays a role in bone metabolism and homeostasis. OPN not only is an important factor in neuron-mediated and endocrine-regulated bone mass, but also is involved in biological activities such as proliferation, migration, and adhesion of several bone-related cells, including bone marrow mesenchymal stem cells, hematopoietic stem cells, osteoclasts, and osteoblasts. OPN has been demonstrated to be closely related to the occurrence and development of many bone-related diseases, such as osteoporosis, rheumatoid arthritis, and osteosarcoma. As expected, the functions of OPN in the bone have become a research hotspot. In this article, we try to decipher the mechanism of OPN-regulated bone metabolism and bone diseases.

18F-Fluoride Signal Amplification Identifies Microcalcifications Associated With Atherosclerotic Plaque Instability in Positron Emission Tomography/Computed Tomography Images

BACKGROUND

Microcalcifications in atherosclerotic plaques are destabilizing, predict adverse cardiovascular events, and are associated with increased morbidity and mortality.¹⁸F-fluoride positron emission tomography (PET)/computed tomography (CT) imaging has demonstrated promise as a useful clinical diagnostic tool in identifying high-risk plaques; however, there is confusion as to the underlying mechanism of signal amplification seen in PET-positive, CT-negative image regions. This study tested the hypothesis that ¹⁸F-fluoride PET/CT can identify early microcalcifications.

METHODS

¹⁸F-fluoride signal amplification derived from microcalcifications was validated against near-infrared fluorescence molecular imaging and histology using an in vitro 3-dimensional hydrogel collagen platform, ex vivo human specimens, and a mouse model of atherosclerosis.

RESULTS

Microcalcification size correlated inversely with collagen concentration. The ¹⁸F-fluoride ligand bound to microcalcifications formed by calcifying vascular smooth muscle cell derived extracellular vesicles in the in vitro 3-dimensional collagen system and exhibited an increasing signal with an increase in collagen concentration (0.25 mg/mL collagen -33.8×10²±12.4×10² counts per minute; 0.5 mg/mL collagen -67.7×10²±37.4×10² counts per minute; P=0.0014), suggesting amplification of the PET signal by smaller microcalcifications. We further incubated human atherosclerotic endarterectomy specimens with clinically relevant concentrations of ¹⁸F-fluoride. The ¹⁸F-fluoride ligand labeled microcalcifications in PET-positive, CT-negative regions of explanted human specimens as evidenced by ¹⁸F-fluoride PET/CT imaging, near-infrared fluorescence, and histological analysis. Additionally, the ¹⁸F-fluoride ligand identified micro and macrocalcifications in atherosclerotic aortas obtained from low-density lipoprotein receptor-deficient mice.

CONCLUSIONS

Our results suggest that ¹⁸F-fluoride PET signal in PET-positive, CT-negative regions of human atherosclerotic plaques is the result of developing microcalcifications, and high surface area in regions of small microcalcifications may amplify PET signal.

MicroRNA-638 inhibits human aortic valve interstitial cell calcification by targeting Sp7

Calcific aortic valve disease (CAVD) is a complex heart valve disease involving a wide range of pathological changes. Emerging evidence indicates that osteogenic differentiation of human aortic valve interstitial cells (hAVICs) plays a key role in valve calcification. In this study, we aimed to investigate the function of miR-638 in hAVICs osteogenesis. Both miRNA microarray assay and qRT-PCR results demonstrating miR-638 was obviously up-regulated in calcific aortic valves compared with non-calcific valves. We also proved that miR-638 was significantly up-regulated during hAVICs osteogenic differentiation. Overexpression of miR-638 suppressed osteogenic differentiation of hAVICs in vitro, whereas down-regulation of miR-638 enhance the process. Target prediction analysis and dual-luciferase reporter assay confirmed that Sp7 transcription factor (Sp7) was a direct target of miR-638. Furthermore, knockdown of Sp7 inhibited osteogenic differentiation of hAVICs, which is similar to the results observed in up-regulation miR-638. Our data indicated that miR-638 plays an inhibitory role in hAVICs osteogenic differentiation, which may act by targeting Sp7. MiR-638 may be a potential therapeutic target for CAVD.

Ectopic mineralization in heart valves: new insights from in vivo and in vitro procalcific models and promising perspectives on noncalcifiable bioengineered valves

Ectopic calcification of native and bioprosthetic heart valves represents a major public health problem causing severe morbidity and mortality worldwide. Valve procalcific degeneration is known to be caused mainly by calcium salt precipitation onto membranes of suffering non-scavenged cells and dead-cell-derived products acting as major hydroxyapatite nucleators. Although etiopathogenesis of calcification in native valves is still far from being exhaustively elucidated, it is well known that bioprosthesis mineralization may be primed by glutaraldehyde-mediated toxicity for xenografts, cryopreservation-related damage for allografts and graft immune rejection for both. Instead, mechanical valves, which are free from calcification, are extremely thrombogenic, requiring chronic anticoagulation therapies for transplanted patients. Since surgical substitution of failed valves is still the leading therapeutic option, progressive improvements in tissue engineering techniques are crucial to attain readily available valve implants with good biocompatibility, proper functionality and long-term durability in order to meet the considerable clinical demand for valve substitutes. Bioengineered valves obtained from acellular non-valvular scaffolds or decellularized native valves are proving to be a compelling alternative to mechanical and bioprosthetic valve implants, as they appear to permit repopulation by the host's own cells with associated tissue remodelling, growth and repair, besides showing less propensity to calcification and adequate hemodynamic performances. In this review, insights into valve calcification onset as revealed by in vivo and in vitro procalcific models are updated as well as advances in the field of valve bioengineering.

Recent Advances on Relationship Between Inorganic Phosphate and Pathologic Calcification: Is Calcification After Breast Augmentation with Fat Grafting Correlated with Locally Increased Concentration of Inorganic Phosphate?

BACKGROUND

Pathologic calcification has frequently occurred after breast augmentation with fat grafting as well as other conditions such as breast cancer, trauma, myocardial infarction, arteriosclerosis and even after reduction mammoplasty. Inorganic phosphate, correlated with fat metabolism, is an important factor that induces pathologic calcification such as vascular calcification.

METHODS

A literature search was conducted using PubMed with the keywords: calcification, inorganic phosphate, fat. Studies related to the process of pathologic calcification, correlation between inorganic phosphate and pathologic calcification, between inorganic phosphate and fat metabolism in pathologic calcification were collected.

RESULTS

Various mechanisms were referred to in pathologic calcification among which inorganic phosphate played an important role. Inorganic phosphate could be liberated, under the effect of various enzymes, in the process of fat metabolism. The authors hypothesized that a large-scale necrotizing zone, which could occur in fat grafting with large amounts per cannula, might provide a high-phosphate environment which might contribute to differentiation of surrounding cells such as stem cells or regenerated vessel cells into osteoblast-like cells that induce pathologic calcification.

CONCLUSION

Inorganic phosphate, which was correlated with fat metabolism, played a significant role in pathologic calcification. We firstly hypothesize that calcification after fat grafting may be related to locally increasing concentrations of phosphate in a necrotizing zone. Further research should be conducted to verify this hypothesis.

LEVEL OF EVIDENCE V

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Vascular ossification: Pathology, mechanisms, and clinical implications

In recent years, the mechanisms and clinical significance of vascular calcification have been increasingly investigated. For over a century, however, pathologists have recognized that vascular calcification is a form of heterotopic ossification. In this review, we aim to describe the pathology and molecular processes of vascular ossification, to characterize its clinical significance and treatment options, and to elucidate areas that require further investigation. The molecular mechanisms of vascular ossification involve the activation of regulators including bone morphogenic proteins and chondrogenic transcription factors and the loss of mineralization inhibitors like fetuin-A and pyrophosphate. Although few studies have examined the gross pathology of vascular ossification, the presence of these molecular regulators and evidence of microfractures and cartilage have been demonstrated on heart valves and atherosclerotic plaques. These changes are often triggered by common inflammatory and metabolic disorders like diabetes, hyperlipidemia, and chronic kidney disease. The increasing prevalence of these diseases warrants further research into the clinical significance of vascular ossification and future treatment options.

Blood, tissue and imaging biomarkers in calcific aortic valve stenosis: past, present and future

PURPOSE OF REVIEW

Calcific aortic valve stenosis is the most prevalent valvular heart disease in the high-income countries. To this date, no medical therapy has been proven to prevent or to stop the progression of aortic valve stenosis. The physiopathology of aortic valve stenosis is highly complex and involves several signalling pathways, as well as genetic related factors, which delay the elaboration of effective pharmacotherapies. Moreover, it is difficult to predict accurately the progression of the valve stenosis and finding the optimal timing for aortic valve replacement remains challenging. Therefore, the present review makes an inventory of the most recent and promising circulating and imaging biomarkers related to the underlying mechanisms involved in the physiopathology of aortic valve stenosis, as well as the biomarkers associated with the left ventricular (LV) remodelling and subsequent dysfunction in patients with aortic valve stenosis.

RECENT FINDINGS

Over the last decade, several blood, tissue and imaging biomarkers have been investigated in aortic valve stenosis patients. At the aortic valve level, these biomarkers are mostly associated and/or involved with processes such as lipid infiltration and oxidation, chronic inflammation and fibrocalcific remodelling of the valve. Moreover, recent findings suggest that aging and sex hormones might interact with these multiple processes. Several studies demonstrated the usefulness of circulating biomarkers such as lipoprotein(a), brain natriuretic peptides and high-sensitivity cardiac troponin, which are very close to clinical routine. Furthermore, noninvasive imaging biomarkers including positron emission tomography and cardiac magnetic resonance, which provide a detailed view of the disease activity within the aortic valve and its repercussion on the left ventricle, may help to improve the understanding of aortic valve stenosis physiopathology and enhance the risk stratification. Other biomarkers such as von Willebrand factor and microRNAs are promising but further studies are needed to prove their additive value in aortic valve stenosis.

SUMMARY

Most of the biomarkers are used in research and thus, are still being investigated. However, some biomarkers including plasma level of lipoprotein(a), F-sodium fluoride, brain natriuretic peptides and high-sensitivity cardiac troponin can be or are very close to be used for the clinical management of patients with aortic valve stenosis. Moreover, a multibiomarker approach might provide a more global view of the disease activity and improve the management strategies of these patients.

Combination of biomarkers of vascular calcification and sTWEAK to predict cardiovascular events in chronic kidney disease

BACKGROUND AND AIMS

Vascular calcification (VC) and atherosclerosis are associated with an increased cardiovascular morbimortality in chronic kidney disease (CKD). Osteoprotegerin (OPG) and osteopontin (OPN) are involved in both VC and CKD. Soluble tumor necrosis factor-like weak inducer of apoptosis (sTWEAK) has been related to cardiovascular disease. We hypothesized that OPG, OPN and sTWEAK levels may be associated with a higher prevalence of cardiovascular outcomes in patients with CKD.

METHODS

The presence of calcified or non-calcified atherosclerotic plaques was assessed in 1043 stage 3 to 5D CKD patients from The NEFRONA Study. Biochemical measurements and OPG, OPN and sTWEAK serum levels were analyzed. Patients were followed for cardiovascular outcomes (41 ± 16 months).

RESULTS

At recruitment, 26% of CKD patients had VC. The adjusted odds ratios for having VC were 2.22 (1.32-3.75); p=.003 for OPG, and 0.45 (0.24-0.84); p=.01 for sTWEAK concentrations. After follow-up, 95 CV events occurred. In a Cox model, patients with OPG or OPN above and sTWEAK below their optimal cut-off points had an adjusted higher risk of cardiovascular events [HR: 2.10 (1.49-3.90); p=.02; 1.65 (1.02-2.65); p=.04; 2.05 (1.28-3.29), p=.003; respectively]. When CKD patients were grouped according to the number of biomarkers above (OPG and OPN) or below (sTWEAK) their cut-off points, the combination of these biomarkers showed the highest risk for cardiovascular events [HR: 9.46 (3.80-23.5) p < .001]. A composite score of these three biomarkers increased the C-statistic and net reclassification index beyond conventional risk factors and VC.

CONCLUSIONS

The combination of OPG, OPN and sTWEAK increased the predictability of cardiovascular outcomes.

Assessment of aortic valve calcium load by multidetector computed tomography. Anatomical validation, impact of scanner settings and incremental diagnostic value

OBJECTIVES

To validate aortic valve calcium (AVC) load measurements by multidetector row computed tomography (MDCT), to evaluate the impact of tube potential and slice thickness on AVC scores, to examine the accuracy of AVC load in distinguishing severe from nonsevere aortic stenosis (AS) and to investigate its effectiveness as an alternative diagnosis method when echocardiography remains inconclusive.

METHODS

We prospectively studied 266 consecutive patients with moderate to severe AS who underwent MDCT to measure AVC load and a comprehensive echocardiographic examination to assess AS severity. AVC load was validated against valve weight in 57 patients undergoing aortic valve replacement. The dependence of AVC scores on tube potential and slice thickness was also tested, as well as the relationship between AVC load and echocardiographic criteria of AS severity.

RESULTS

MDCT Agatston score correlated well with valve weight (r = 0.82, p < 0.001) and hemodynamic indices of AS severity (all p < 0.001). Ex-vivo Agatston scores decreased significantly with increasing tube potential and slice thickness (repeated measures ANOVA p < 0.001). Multivariate analysis identified mean gradient, the indexed effective orifice area, male gender and left ventricular outflow tract cross-sectional area as independent correlates of the in-vivo AVC load.

CONCLUSIONS

MDCT-derived AVC load correlated well with valve weight and hemodynamic indices of AS severity. It also depends on tube potential and slice thickness, thus suggesting that these parameters should be standardized to optimize reproducibility and accuracy.

Sex-dependent aortic valve pathology in patients with rheumatic heart disease

Background

Rheumatic heart disease is an autoimmune disease caused by group A streptococci infection and frequently affects the aortic valve. Sex differences are common in the disease progression, treatment, and outcome. However, little is known about the sex differences in the pathology of aortic valves in rheumatic heart disease.

Design

We studied the end-stage calcific aortic valves from male versus female patients to reveal the sex-dependent pathology differences and molecular changes associated with requiring valve replacement.

Methods

Aortic valves from 39 patients with rheumatic heart disease (19 males and 20 females) were collected at the time of aortic valve replacement for comparative pathology, immunohistochemistry, and gene expression analyses. Clinical characteristics were also analyzed and compared between the two groups.

Results

Aortic valves from female patients exhibited increased expression of collagens, infiltration of monocytes/macrophages and neovascularization. Aortic valves from female patients also had increased expression of inflammatory genes involved in the NFKB pathway (phosphorylated NFKB p65 subunit, IL8, and NOS3) and Th1 cytokine genes (IFNA and IL12B). The severe valve pathology in female patients was correlated with a higher serum level of anti-streptolysin O antibodies.

Conclusion

Inflammation is more prominent in aortic valves of female patients with rheumatic heart disease. This sex difference may contribute to the severe valve pathology and worse outcome of female patients.

SERUM OSTEOPONTIN LEVEL IS ASSOCIATED WITH PRESENCE OF ATRIAL FIBRILLATION IN CALCIFIC AORTIC VALVE STENOSIS

Identification of risk factors associated with presence of atrial fibrillation (AF) in patients with aortic valve stenosis (AS) remains to be unraveled.The aim of the study was to investigate relationship between profibrotic biomarkers and presence of AF in AS patientsMethods. 191 patients (29,8% male, 77,7±0,59 years) with AS (defined as aortic valve area (AVA) ≤ 2,0 sm2) were enrolled in the study. Clinical, echocardiographic and biochemical variables, including serum TGFβ1 and osteopontin levels were compared between 2 groups of patients: with and without AF. Results. 83(36,5%) of AS patients had AF. In logistic regression models independent associations between AVA index (p=0,040), left atrial volume (p=0,021), OPN (р=0,009) and presence of AF were found. Patients with serum OPN level > 10,05 ng/ml had twice more higher AF incidence comparedto patients with serum OPN level ≤ 10,05 ng/ml (53,8% and 29,2%, respectively, p=0,020).Conclusion. Serum OPN level was independently associated with presence of AF in AS patients, thus we speculate on it’s predominant profibrotic role in the left atrium.

Arterial Calcification in Diabetes Mellitus: Preclinical Models and Translational Implications

Diabetes mellitus increasingly afflicts our aging and dysmetabolic population. Type 2 diabetes mellitus and the antecedent metabolic syndrome represent the vast majority of the disease burden-increasingly prevalent in children and older adults. However, type 1 diabetes mellitus is also advancing in preadolescent children. As such, a crushing wave of cardiometabolic disease burden now faces our society. Arteriosclerotic calcification is increased in metabolic syndrome, type 2 diabetes mellitus, and type 1 diabetes mellitus-impairing conduit vessel compliance and function, thereby increasing the risk for dementia, stroke, heart attack, limb ischemia, renal insufficiency, and lower extremity amputation. Preclinical models of these dysmetabolic settings have provided insights into the pathobiology of arterial calcification. Osteochondrogenic morphogens in the BMP-Wnt signaling relay and transcriptional regulatory programs driven by Msx and Runx gene families are entrained to innate immune responses-responses activated by the dysmetabolic state-to direct arterial matrix deposition and mineralization. Recent studies implicate the endothelial-mesenchymal transition in contributing to the phenotypic drift of mineralizing vascular progenitors. In this brief overview, we discuss preclinical disease models that provide mechanistic insights-and point to challenges and opportunities to translate these insights into new therapeutic strategies for our patients afflicted with diabetes mellitus and its arteriosclerotic complications.

Osteopontin alters endothelial and valvular interstitial cell behaviour in calcific aortic valve stenosis through HMGB1 regulation

OBJECTIVES

Calcific aortic valve stenosis (CAVS) is an important clinical problem predominantly affecting elderly individuals. Studies suggest that the progression of CAVS is actively regulated with valve endothelial injury leading to inflammation, fibrosis and calcification. The aim of this study was to delineate the possible regulatory role of osteopontin (OPN) on high-mobility group box 1 (HMGB1) function and the associated inflammatory and fibrotic response in CAVS.

METHODS

Aortic valve leaflets were collected from CAVS patients undergoing aortic valve replacement (n = 40), and control aortic valve leaflets were obtained from heart transplant recipients (n = 15). Valves and plasma were analysed by quantitative real-time polymerase chain reaction (PCR), immunohistochemical staining and Western blot. Recombinant OPN or neutralizing OPN antibody was added to cultured endothelial and valvular interstitial cells (VICs), and cell proliferation scores and HMGB1 expression were assessed.

RESULTS

CAVS valves had a decreased total percentage of VICs but increased numbers of infiltrating macrophages relative to control valves. RT-PCR studies showed higher expression of OPN, the inflammatory cytokine tumour necrosis factor-alpha as well as markers of fibrosis, tissue inhibitor of matrix metalloproteinase 1 and matrix metalloproteinase 2 in CAVS valves. Elevated expression of OPN was also observed in plasma of CAVS patients compared with controls. HMGB1 was detected in the secretory granules of cultured valve endothelial and VICs derived from CAVS valves. The addition of exogenous OPN inhibited the proliferation of cultured endothelial and VICs from CAVS valves and was associated with the extracellular expression of HMGB1, whereas neutralizing OPN had the opposite effect.

CONCLUSIONS

We conclude that altered OPN expression in CAVS affects cellular HMGB1 function inducing cytoplasmic translocation and secretion of HMGB1 in endothelial cells and VICs, thus indicating a regulatory role for OPN in the progression of CAVS through alteration of HMGB1 function.

Serum osteopontin level and common carotid artery intima-media wall thickness in psoriasis

BACKGROUND

The association between psoriasis and cardiovascular disease is well documented, but the underlying mechanisms remain unknown. The relationship between osteopontin and psoriasis has been studied. High serum levels of osteopontin are reported in psoriasis, with increased cardiovascular risk factors in these patients.

OBJECTIVES

We evaluate the extent of subclinical atherosclerosis by measuring the mean intima-media wall thickness (MIMT) of the common carotid artery (CCA) in patients with psoriasis and assessing its correlation with osteopontin to identify vascular risk factors associated with psoriasis.

METHODS

Intima-media wall thickness of the CCA and plasma osteopontin were determined in 40 patients and 40 age- and sex-matched healthy control subjects.

RESULTS

Median serum osteopontin was significantly higher in patients with psoriasis than in healthy control subjects. Mean intima-media wall thickness of the CCA was positively associated with plasma osteopontin level (r = 0.47, P < 0.0001), body mass index (r = 0.62, P < 0.0001), age (r = 0.54, P < 0.0001), total cholesterol (r = 0.54, P < 0.0001), and triglycerides (r = 0.65, P < 0.0001).

CONCLUSIONS

This study shows higher levels of plasma osteopontin and MIMT-CCA in psoriasis patients than in healthy controls. This is the first study to show a positive correlation between plasma osteopontin and MIMT-CCA.

F-18 Fluoride Positron Emission Tomography-Computed Tomography for Detecting Atherosclerotic Plaques

A large number of major cardiovascular events occur in patients due to minimal or some lumen narrowing of the coronary artery. Recent biological studies have shown that the biological composition or vulnerability of the plaque is more critical for plaque rupture compared to the degree of stenosis. To overcome the limitations of anatomical images, molecular imaging techniques have been suggested as promising imaging tools in various fields. F-18 fluorodeoxyglucose (FDG), which is widely used in the field of oncology, is an example of molecular probes used in atherosclerotic plaque evaluation. FDG is a marker of plaque macrophage glucose utilization and inflammation, which is a prominent characteristic of vulnerable plaque. Recently, F-18 fluoride has been used to visualize vulnerable plaque in clinical studies. F-18 fluoride accumulates in regions of active microcalcification, which is normally observed during the early stages of plaque formation. More studies are warranted on the accumulation of F-18 fluoride and plaque formation/vulnerability; however, due to high specific accumulation, low background activity, and easy accessibility, F-18 fluoride is emerging as a promising non-invasive imaging probe to detect vulnerable plaque.

Osteopontin mediates mineralization and not osteogenic cell development in vitro

Biomineralization is a complex process in the development of mineralized tissues such as bone and pathological calcifications such as atherosclerotic plaques, kidney stones and gout. Osteopontin (OPN), an anionic phosphoprotein, is expressed in mineralizing tissues and has previously been demonstrated to be a potent inhibitor of hydroxyapatite formation. The OPN-deficient (Opn-/-) mouse displays a hypermineralized bone phenotype starting at 12 weeks postnatally. By isolating and culturing Opn-/- and wild-type (WT) osteoblasts, we sought to determine the role of OPN and two of its functional peptides in osteoblast development and mineralization. Opn-/- osteoblasts had significantly increased mineral deposition relative to their WT counterparts, with no physiologically relevant change in gene expression of osteogenic markers. Supplementation with bovine milk OPN (mOPN) led to a dramatic reduction in mineral deposition by the Opn-/- osteoblasts. Treatment with OPN-derived peptides corresponding to phosphorylated OPN-(220-235) (P3) and non-phosphorylated OPN-(65-80) (OPAR) also rescued the hypermineralization phenotype of Opn-/- osteogenic cultures. Supplementation with mOPN or the OPN-derived peptides did not alter the expression of terminal osteogenic markers. These data suggest that OPN plays an important role in the regulation of biomineralization, but that OPN does not appear to affect osteoblast cell development in vitro.

miR-30e targets IGF2-regulated osteogenesis in bone marrow-derived mesenchymal stem cells, aortic smooth muscle cells, and ApoE-/- mice

AIMS

Activation of an osteogenic transcriptional program contributes to the initiation of aortic calcification in atherosclerosis. The role of microRNAs in regulating aortic calcification is understudied. We tested the hypothesis that miR-30e regulates an osteogenic program in bone marrow-derived mesenchymal stem cells (MSCs), aortic smooth muscle cells (SMCs), and ApoE(-/-) mice.

METHODS AND RESULTS

In aortas of wild-type mice, we found that miR-30e is highly expressed in medial SMCs. In aortas of old ApoE(-/-) mice, we found that miR-30e transcripts are down-regulated in an inverse relation to the osteogenic markers Runx2, Opn, and Igf2. In vitro, miR-30e over-expression reduced the proliferation of MSCs and SMCs while increasing adipogenic differentiation of MSCs and smooth muscle differentiation of SMCs. In MSCs and SMCs over-expressing miR-30e, microarrays and qPCR showed repression of an osteogenic gene panel including Igf2. Inhibiting miR-30e in MSCs increased Igf2 transcripts. In SMCs, IGF2 recombinant protein rescued miR-30e-repressed osteogenic differentiation. Luciferase and mutagenesis assays showed binding of miR-30e to a novel and essential site at the 3'UTR of Igf2. In ApoE(-/-) mice, injections of antimiR-30e oligos increased Igf2 expression in the aortas and livers and significantly enhanced OPN protein expression and calcium deposition in aortic valves.

CONCLUSION

miR-30e represses the osteogenic program in MSCs and SMCs by targeting IGF2 and drives their differentiation into adipogenic or smooth muscle lineage, respectively. Our data suggest that down-regulation of miR-30e in aortas with age and atherosclerosis triggers vascular calcification. The miR-30e pathway plays an important regulatory role in vascular diseases.

Regulation of valve endothelial cell vasculogenic network architectures with ROCK and Rac inhibitors

OBJECTIVE

The age- and disease-dependent presence of microvessels within heart valves is an understudied characteristic of these tissues. Neovascularization involves endothelial cell (EC) migration and cytoskeletal reorientation, which are heavily regulated by the Rho family of GTPases. Given that valve ECs demonstrate unique mesenchymal transdifferentiation and cytoskeletal mechanoresponsiveness, compared to vascular ECs, this study quantified the effect of inhibiting two members of the Rho family on vasculogenic network formation by valve ECs.

APPROACH AND RESULTS

A tubule-like structure vasculogenesis assay (assessing lacunarity, junction density, and vessel density) was performed with porcine aortic valve ECs treated with small molecule inhibitors of Rho-associated serine-threonine protein kinase (ROCK), Y-27632, or the Rac1 inhibitor, NSC-23766. Actin coordination, cell number, and cell migration were assessed through immunocytochemistry, MTT assay, and scratch wound healing assay. ROCK inhibition reduced network lacunarity and interrupted proper cell-cell adhesion and actin coordination. Rac1 inhibition increased lacunarity and delayed actin-mediated network formation. ROCK inhibition alone significantly inhibited migration, whereas both ROCK and Rac1 inhibition significantly reduced cell number over time compared to controls. Compared to a vascular EC line, the valve ECs generated a network with larger total vessel length, but a less smooth appearance.

CONCLUSIONS

Both ROCK and Rac1 inhibition interfered with key processes in vascular network formation by valve ECs. This is the first report of manipulation of valve EC vasculogenic organization in response to small molecule inhibitors. Further study is warranted to comprehend this facet of valvular cell biology and pathology and how it differs from vascular biology.

The stretch responsive microRNA miR-148a-3p is a novel repressor of IKBKB, NF-κB signaling, and inflammatory gene expression in human aortic valve cells

Bicuspid aortic valves calcify at a significantly higher rate than normal aortic valves, a process that involves increased inflammation. Because we have previously found that bicuspid aortic valve experience greater stretch, we investigated the potential connection between stretch and inflammation in human aortic valve interstitial cells (AVICs). Microarray, quantitative PCR (qPCR), and protein assays performed on AVICs exposed to cyclic stretch showed that stretch was sufficient to increase expression of interleukin and metalloproteinase family members by more than 1.5-fold. Conditioned medium from stretched AVICs was sufficient to activate leukocytes. microRNA sequencing and qPCR experiments demonstrated that miR-148a-3p was repressed in both stretched AVICs (43% repression) and, as a clinical correlate, human bicuspid aortic valves (63% reduction). miR-148a-3p was found to be a novel repressor of IKBKB based on data from qPCR, luciferase, and Western blot experiments. Furthermore, increasing miR-148a-3p levels in AVICs was sufficient to decrease NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) signaling and NF-κB target gene expression. Our data demonstrate that stretch-mediated activation of inflammatory pathways is at least partly the result of stretch-repression of miR-148a-3p and a consequent failure to repress IKBKB. To our knowledge, we are the first to report that cyclic stretch of human AVICs activates inflammatory genes in a tissue-autonomous manner via a microRNA that regulates a central inflammatory pathway.

Impact of valve surgery on serum osteopontin levels in patients with mitral regurgitation

OBJECTIVE

Osteopontin (OPN), a sialoprotein present within atherosclerotic lesions, especially in calcified plaques, is linked to the progression of coronary artery disease and heart failure. We assessed the impact of valve surgery on serum OPN and left ventricular (LV) function in patients with mitral regurgitation (MR).

METHODS

Thirty-two patients with severe MR scheduled for surgery were included in the study. Echocardiography markers were assessed preoperatively and at 3 months following the surgery and matched with the serum OPN levels.

RESULTS

Valve surgery was associated with a reduction of the ejection fraction (EF) from 55.2 ± 6.3 to 48.8 ± 7.1% after surgery, p < 0.001. Following surgery, the OPN level was significantly higher than preoperatively (mean 245, range 36-2,284 ng/ml vs. 76, 6-486 ng/ml, p = 0.007). Preoperative OPN exhibited a slight negative correlation with the EF (r = -0.35, p = 0.04), and a moderate correlation with vena contracta (r = -0.38, p = 0.02). There were no other meaningful correlations between conventional echocardiographic parameters and OPN.

CONCLUSION

Following valve surgery due to severe MR, patients exhibited a decrease in EF and an increase in OPN levels. The assessment of preoperative OPN failed to strongly predict probable LV dysfunction.